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Identification and remediation of oversensed cardiac events using far-field electrograms


Title: Identification and remediation of oversensed cardiac events using far-field electrograms.
Abstract: In general, the disclosure is directed to techniques for identification and remediation of oversensed cardiac events using far-field electrograms (FFEGMs). Identification of oversensed cardiac events can be used in an ICD to prevent ventricular fibrillation (VF) detection, and thereby avoid delivery of an unnecessary defibrillation shock. Alternatively, or additionally, identification of oversensed cardiac events can be used in an ICD to support delivery of bradycardia pacing during an oversensing condition. In some cases, bradycardia pacing delivered in response to detection of oversensed cardiac events may include pacing pulses from multiple vectors to provide redundancy in the event the oversensing may be due to a lead-related condition. ...

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USPTO Applicaton #: #20100106209 - Class: $ApplicationNatlClass (USPTO) -
Inventors: Bruce D. Gunderson, Donald James Ruzin



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The Patent Description & Claims data below is from USPTO Patent Application 20100106209, Identification and remediation of oversensed cardiac events using far-field electrograms.

TECHNICAL FIELD

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The disclosure relates to implantable medical devices (IMDs), and, more particularly, to detection of oversensed cardiac events by implantable medical devices.

BACKGROUND

A variety of implantable medical devices (IMDs) for delivering a therapy have been clinically implanted or proposed for clinical implantation in patients. Some implantable medical devices may employ one or more elongated electrical leads carrying stimulation electrodes, sense electrodes, and/or other sensors. Implantable medical devices may deliver therapy or monitor conditions with respect to a variety of organs, nerves, muscle or tissue, such as the heart, brain, stomach, spinal cord, pelvic floor, or the like. Implantable medical leads may be configured to allow electrodes or other sensors to be positioned at desired locations for delivery of electrical stimulation or sensing of physiological conditions. For example, electrodes or sensors may be carried at a distal portion of a lead. A proximal portion of the lead may be coupled to an implantable medical device housing, which may contain circuitry such as signal generation circuitry and/or sensing circuitry.

Some IMDs, such as cardiac pacemakers or implantable cardioverter-defibrillators (ICDs), provide therapeutic electrical stimulation to the heart via electrodes carried by one or more implantable leads. The electrical stimulation may include signals such as pacing pulses, cardioversion shocks, or defibrillation shocks to address abnormal cardiac rhythms such as bradycardia, tachycardia, or fibrillation. In some cases, an IMD may sense intrinsic depolarizations of the heart to identify normal or abnormal rhythms. Upon detection of an abnormal rhythm, the device may deliver an appropriate electrical stimulation signal or signals to restore or maintain a more normal rhythm. For example, in some cases, an IMD may deliver pacing pulses to the heart upon detecting tachycardia or bradycardia, and deliver cardioversion or defibrillation shocks to the heart upon detecting tachycardia or fibrillation.

Leads associated with an IMD typically include a lead body containing one or more elongated electrical conductors that extend through the lead body from a connector assembly provided at a proximal lead end to one or more electrodes located at the distal lead end or elsewhere along the length of the lead body. The conductors connect stimulation and/or sensing circuitry within an associated IMD housing to respective electrodes or sensors. Some electrodes may be used for both stimulation and sensing, while other electrodes may be dedicated to only stimulation or only sensing. Each electrical conductor is typically electrically isolated from other electrical conductors, and is encased within an outer sheath that electrically insulates the lead conductors from body tissue and fluids.

Cardiac lead bodies tend to be continuously flexed by the beating of the heart. Other stresses may be applied to the lead body during implantation or lead repositioning. Patient movement can cause the route traversed by the lead body to be constricted or otherwise altered, causing stresses on the lead body. The electrical connection between implantable medical device connector elements and the lead connector elements can be intermittently or continuously disrupted. Connection mechanisms, such as set screws, may be insufficiently tightened at the time of implantation, followed by a gradual loosening of the connection. Also, lead pins may not be completely inserted. In some cases, changes in leads or connections may result in intermittent or continuous changes in lead impedance.

Short circuits, open circuits or significant changes in impedance may be referred to, in general, as lead-related conditions. In the case of cardiac leads, sensing of an intrinsic heart rhythm through a lead can be altered by lead-related conditions. Structural modifications to leads, conductors or electrodes may alter sensing integrity. Furthermore, impedance changes in the stimulation path due to lead-related conditions may affect sensing and stimulation integrity for pacing, cardioversion, or defibrillation. In addition to lead-related conditions, conditions associated with sensor devices or sensing circuitry, as well as conditions associated with electrodes or sensors not located on leads, may affect sensing integrity. Lead-related conditions, electromagnetic interference (EMI), myopotentials caused by patient movement, or other noise sources may affect sensing integrity. Cardiac events that are falsely detected may be referred to as oversensed cardiac events.

SUMMARY

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In general, the disclosure is directed to techniques for identification and remediation of oversensed cardiac events in an IMD. The techniques may make use of far-field electrograms (FFEGMs) to identify oversensed cardiac events. Identification of oversensed cardiac events can be used in an IMD to prevent inappropriate ventricular fibrillation (VF) detection, and thereby avoid delivery of an unnecessary defibrillation shock. Alternatively, or additionally, identification of oversensed cardiac events can be used in an IMD to support delivery of bradycardia pacing during an oversensing condition. In some cases, bradycardia pacing delivered in response to detection of oversensed cardiac events may include pacing pulses from multiple stimulation vectors to provide redundancy in the event the oversensing may be due to a lead-related condition. The techniques, in some cases, may repair interval data upon identification of oversensing to support proper operation of defibrillation and/or pacing therapies that are responsive to the interval data.

In one example, the disclosure provides a method comprising acquiring a first cardiac signal via a first sense electrode configuration, acquiring a second cardiac signal via a second sense electrode configuration, detecting cardiac events in the first cardiac signal, identifying at least some of the cardiac events detected in the first cardiac signal as oversensed events based on whether one or more characteristics of the second cardiac signal confirm the cardiac events, and controlling delivery of cardiac electrical stimulation therapy to a patient based on the identification of the oversensed events.

In another example, the disclosure provides an implantable medical device comprising an electrical sensing module configured to acquire first cardiac signal via a first sense electrode configuration, and acquire a second cardiac signal via a second sense electrode configuration, a stimulation module configured to deliver cardiac electrical stimulation therapy to a patient via stimulation electrodes, and a processor configured to detect cardiac events in the first cardiac signal, identify at least some of the cardiac events detected in the first cardiac signal as oversensed events based on whether one or more characteristics of the second cardiac signal confirm the cardiac events, and control the stimulation module to deliver the cardiac electrical stimulation therapy to the patient based on the identification of the oversensed events.

In another example, the disclosure provides a computer-readable storage medium comprising instructions that, when executed by a processor in an implantable medical device, cause the processor to detect cardiac events in a first cardiac signal acquired via a first sense electrode configuration, identify at least some of the cardiac events detected in the first cardiac signal as oversensed events based on whether one or more characteristics of a second cardiac signal acquired via a second sense electrode configuration confirm the cardiac events, and control a stimulation module to deliver of cardiac electrical stimulation therapy to a patient based on the identification of the oversensed events.

The details of one or more aspects of the disclosure are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will be apparent from the description and drawings, and from the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

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FIG. 1 is a conceptual diagram illustrating a therapy system comprising an implantable medical device (IMD) in the form of an implantable cardioverter defibrillator (ICD) for delivering stimulation therapy to a heart of a patient via implantable leads.

FIG. 2 is a conceptual diagram further illustrating the ICD and leads of the system of FIG. 1 in conjunction with the heart.

FIG. 3 is a conceptual diagram illustrating another example therapy system comprising the ICD of FIG. 1 coupled to a different configuration of leads.

FIG. 4 is a functional block diagram illustrating example components of the ICD of FIG. 1.

FIG. 5 is a functional block diagram illustrating an example electrical sensing module of the ICD of FIG. 1.

FIG. 6 is a flow diagram illustrating a method for identification and remediation of oversensed cardiac event.

FIG. 7 is a flow diagram illustrating an example of the use of far-field electrogram (FFEGM) amplitude analysis in the method of FIG. 6.

FIG. 8 is a graph illustrating a technique for identification and remediation of oversensed cardiac events using an FFEGM to inhibit delivery of an inappropriate defibrillation shock.

FIG. 9 is a graph illustrating a technique for identification and remediation of oversensed cardiac events using an FFEGM to permit delivery of a bradycardia pacing pulse.

FIG. 10 is a graph illustrating another technique for identification and remediation of oversensed cardiac events using an FFEGM to permit delivery of a bradycardia pacing pulse and immediate backup pacing pulse.

FIG. 11 is a graph illustrating an additional technique for identification and remediation of oversensed cardiac events using an FFEGM to permit delivery of a bradycardia pacing pulse and immediate backup pacing pulse.

DETAILED DESCRIPTION

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In general, the disclosure is directed to techniques for identification and remediation of oversensed cardiac events using far-field electrograms (FFEGMs). Lead-related conditions (e.g. fracture, insulation breach, loose set screw, or the like), EMI, myopotentials, or other noise sources may produce noise that causes oversensing of cardiac events, i.e., false detection of cardiac events. Oversensing of cardiac events due to noise can affect the operation of an IMD such as an implantable cardioverter defibrillator (ICD).

An oversensed event may refer, generally, to any cardiac event that is falsely detected due to any of a variety of factors, such as the noise sources described above. The oversensed event does not generally represent an actual physiological event within the heart, such as a ventricular depolarization (R wave), but instead an artifact of a noise source, such as a fractured conductor in a lead or some other lead-related condition. In contrast, a valid, detected cardiac event will be based on signal characteristics consistent with an actual physiological activity of the heart.

Oversensing may cause an implantable cardioverter defibrillator (ICD) or other IMD to deliver inappropriate cardioversion or defibrillation shocks. In particular, oversensing may result in an erroneous indication of arrhythmia, causing the ICD to deliver an unnecessary shock. Unnecessary shocks can be painful, potentially pro-arrhythmic, and consume excessive amounts of power from finite battery resources.

In addition, in an ICD, oversensing may cause syncope and asystole in pacemaker-dependent patients. Increased numbers of pacemaker-dependent patients are receiving ICDs, including Cardiac Resynchronization Therapy (CRT) devices. Oversensing may cause bradycardia pacing to be inhibited due to an erroneous indication of arrhythmia. For example, during a detected arrhythmia, the ICD may inhibit pacing to avoid affecting detection of ventricular fibrillation, or to avoid the possibility of pacing the patient into ventricular fibrillation.

Also, if the noise source is a fractured lead, in addition to causing oversensing, there may be an added risk of failure to capture the heart with a pacing pulse due to a compromised conductor. In this case, even if pacing is not inhibited, syncope and asystole may still be a concern if the same conductor used to sense cardiac events is also used to deliver cardioversion, defibrillation or pacing therapy to the patient.

Noise may cause oversensing on individual sensing vectors or multiple sensing vectors. A sensing vector generally refers to an electrode configuration comprising a combination of electrodes used to sense a cardiac signal. Lead-related conditions may cause oversensing on a single lead or on limited set of sensing vectors. Fracture of a conductor within a lead may cause oversensing on a particular sensing vector comprising a particular combination of electrodes associated with the lead. However, the oversensing may not affect other sensing vectors that do not rely on electrodes coupled to the fractured conductor.

In accordance with some aspects of this disclosure, an ICD may use different sensing vectors comprising different electrode configurations to identify oversensing on another sensing vector. For example, a far-field electrogram (FFEGM) may be used to identify oversensing in a near-field electrogram (NFEGM). A NFEGM may refer, for example, to an electrogram obtained via a particular, near-field set of electrodes carried by one or more leads. An FFEGM may refer to an electrogram obtained via a different, far-field set of electrodes carried by the same lead or different leads.

The far-field set of electrodes may be positioned at some distance from the near-field set of electrodes, e.g., using one or more electrodes on the same lead as the electrodes used to obtain the NFEGM, on a different lead than the electrodes used to obtain the NFEGM, within the same chamber as the electrodes used to obtain the NFEGM, or within a different chamber than the electrodes used to obtain the NFEGM.

If the primary sensing electrode configuration used to obtain the NFEGM is formed by a tip electrode and ring electrode on a right ventricular lead, for example, the FFEGM electrode sensing configuration may include electrodes in any of a wide variety positions, including without limitation other electrodes on right ventricular lead, electrodes on a left ventricular lead, electrodes on an atrial lead, including various bipolar and unipolar combinations.

In some cases, the sensing electrode configurations used to obtain the FFEGM signal may advantageously include electrodes that are coupled to different lead conductors than the electrodes used to obtain the NFEGM signal, thereby bypassing potential lead faults that may cause oversensed events in the NFEGM signal. In other cases, the sensing electrode configurations used to obtain the FFEGM signal may share one electrode in common with the sensing electrode configuration used to obtain the NFEGM signal.

One example of a NFEGM is a right ventricular NFEGM obtained via a tip electrode and ring electrode of an implantable cardioverter defibrillator (ICD) lead implanted within a patient. For this NFEGM, one example of a FFEGM with respect to the near-field tip-ring electrode configuration is a FFEGM obtained via a coil electrode on an ICD lead implanted within the patient and a can electrode carried on an ICD housing implanted within the patient. The tip and ring electrodes may be designed to deliver cardiac pacing therapy to the right ventricle of the patient's heart. The coil electrode and can electrode may be designed to deliver defibrillation energy to the right ventricle of the patient's heart. A variety of other electrode configurations may be used to obtain NFEGMs and FFEGMs.

When oversensing is identified, indicating false detection of an arrhythmia, an ICD may trigger delivery of pacing. In accordance with some aspects of this disclosure, the ICD may deliver multiple pacing pulses in short succession. For example, the ICD may deliver first pacing therapy via a first stimulation electrode configuration, and deliver second pacing therapy via a second stimulation electrode configuration. In this manner, the ICD may pace from multiple pacing vectors to provide redundancy in the event the oversensing is caused by a fractured conductor in one of the pacing vectors.

In addition to multi-vector pacing, the ICD may measure lead impedance during, before or following delivery of the pacing pulses to confirm that the lead conductors are intact. If the impedance check indicates a potential lead fracture, the ICD may select a different pacing vector. Delivery of pacing via multiple vectors and impedance-based vector selection may be programmable or automatic features of the ICD. For example, these features may be automatically activated if the ICD patient is pacemaker-dependent, e.g., based on recent or frequent delivery of pacing to the patient.

In other aspects, the ICD may identify detected cardiac events in the NFEGM signal as oversensed events based on one or more characteristics of the FFEGM signal at a time substantially coincident with the respective detected cardiac event. Examples of FFEGM signal characteristics may include an amplitude, slope, variability or other characteristic of the FFEGM signal relative within a timing window substantially coincident with the respective detected cardiac event.

The FFEGM signal is obtained from an electrode sensing configuration that is different from the primary sensing electrode configuration and may provide a signal that is generally unaffected by oversensing in the NFEGM signal. For example, the FFEGM signal may be acquired using a sense electrode configuration that does not involve a source of noise, such as a fractured conductor. Consequently, the FFEGM signal can be used for cross-correlation to determine whether a detected cardiac event is an oversensed event. Once a detected cardiac event is identified as an oversensed event, the ICD may apply a remediation technique to reduce the likelihood of unnecessary shocks or inhibited pacing.

As an example, for remediation, the ICD may adjust an R-R interval tracked for purposes of triggering cardioversion, defibrillation or pacing. The detected cardiac events may be R-waves detected in the NFEGM. The R-R interval indicates the time between successive detected R waves, i.e., successive detected ventricular depolarizations of the heart. Numerous short R-R intervals or varied R-R intervals may indicate the presence of an arrhythmia. Numerous oversensed events may result in numerous short or varied R-R intervals. The ICD may maintain a ventricular fibrillation (VF) count that is calculated at least in part as a function of the number of short R-R intervals (i.e., R-R intervals less than a threshold time period in length) in a given period of time.

When the VF count exceeds a threshold level, the ICD delivers cardioversion or defibrillation. When oversensing causes numerous short R-R intervals, however, the ICD may deliver an inappropriate shock. If R-R intervals are too long, the ICD ordinarily triggers delivery of a bradycardia pacing pulse according to a lower rate interval threshold, thereby providing low rate, backup pacing. When oversensed events produce short R-R intervals, however, there may be no opportunity to reach an R-R interval that triggers pacing. Hence, oversensed events may result in inappropriate shocks as well as inappropriately inhibited pacing. Inhibited pacing in the case of oversensing may result in syncope and asystole.

According to an example remediation technique, an ICD may use identification of oversensed events to keep the VF counter from reaching the number of intervals for detection (NID) threshold, and to reduce the number of short intervals due to oversensing. If the VF counter increments, but does not reach the NID, then a detection and resulting shock is withheld. By eliminating R-R intervals that are caused by oversensed events, the number of erroneous short R-R intervals can be reduced, thereby preventing the VF counter from reaching the NID threshold, and avoiding an unnecessary and inappropriate cardioversion or defibrillation shock.

Eliminating short R-R intervals caused by oversensed events also may have the effect of lengthening R-R intervals to trigger pacing. In particular, the ICD may sum the R-R interval caused by an oversensed event with the R-R interval generated by the next detected cardiac event (e.g., detected R wave) that has not been identified as an oversensed event. This summation of erroneous short intervals will lengthen the R-R intervals, reducing the number of R-R intervals that increment the VF counter. In addition, the R-R intervals will accumulate to produce an overall R-R interval that reaches the length of the lower rate interval that triggers pacing. As one example, the lower rate interval could be approximately two seconds, which corresponds to a pulse rate of thirty beats per minute, and may be sufficient to avoid syncope and asystole. In this manner, the ICD can provide low rate, backup pacing during lead noise, and especially during lead failure.

According to another example remediation technique, an ICD may trigger pacing if at least a minimum number of oversensed R wave events are identified in a given period. For example, in a dual chamber ICD, having atrial and ventricular leads, the ICD may trigger pacing if at least a minimum number of oversensed R wave events are identified since a previous detected atrial event, i.e., a detected P wave, atrial pace or atrial refractory event. The ICD may deliver a pacing pulse after the next detected atrial event, e.g., at a programmed atrial-ventricular (AV) pacing interval (e.g., 250 milliseconds (ms) after the detected atrial event).

In some cases, two or more pacing pulses may be delivered as multiple, short coupled pacing pulses in quick succession, e.g., where a second pulses if deliver 5 to 100 milliseconds (ms) after the initial pacing pulse, using different stimulation vectors (e.g., bipolar, unipolar, left ventricular). During, before or after delivery of each pacing pulse, impedance can be monitored to evaluate the integrity of the stimulation path. Impedance monitoring can be programmed or automatically activated for pacemaker dependent patients, e.g., patients with more than 50% paced beats.

For a single-chamber ICD, i.e., having only a right ventricular lead, the ICD may trigger pacing if at least a minimum number of oversensed R wave events are identified in a specified period of time. The period of time may be, for example, a period of time following a previous non-oversensed R wave event. At the end of the period of time, the ICD may deliver a pacing pulse. Again, the ICD may, in some cases, deliver two or more pacing pulses in quick succession e.g., 5 to 100 milliseconds (ms) apart, using different stimulation vectors, and monitor impedance during each pacing pulse to evaluate the integrity of the stimulation path. In either case, dual or single chamber, the ICD reduces the likelihood that pacing may be inhibited due to oversensed events, and reduces the risk of syncope and asystole as a result of inhibited pacing.

FIG. 1 is a conceptual diagram illustrating an example therapy system 10 that may be used to provide therapy to heart 12 of patient 14. Therapy system 10 includes ICD 16, which is coupled to leads 18, 20, and 22, and programmer 24. ICD 16 may be, for example, a combined implantable pacemaker, cardioverter, defibrillator that provides electrical signals to heart 12 via electrodes coupled to one or more of leads 18, 20, and 22. ICD 16 may be configured to implement various techniques for identification and remediation of oversensed events using FFEGM signals, as described in this disclosure.

Although the oversensing identification and remediation techniques are described with respect to an ICD with support for pacing, cardioversion and defibrillation therapies, they may be implemented in other types of IMDs, such as ICDs without support for pacing therapy or in pacemakers without support for cardioversion or defibrillation therapy. Accordingly, ICD 16 is described for purposes of illustration, and without limitation of the techniques as broadly described in this disclosure.

With further reference to FIG. 1, leads 18, 20, 22 extend into the heart 12 of patient 14 to sense electrical activity of heart 12 and/or deliver electrical stimulation to heart 12. Patient 12 is ordinarily, but not necessarily, a human patient. In the example shown in FIG. 1, right ventricular (RV) lead 18 extends through one or more veins (not shown), the superior vena cava (not shown), and right atrium 26, and into right ventricle 28. Left ventricular (LV) coronary sinus lead 20 extends through one or more veins, the vena cava, right atrium 26, and into the coronary sinus 30 to a region adjacent to the free wall of left ventricle 32 of heart 12. Right atrial (RA) lead 22 extends through one or more veins and the vena cava, and into right atrium 26 of heart 12.

In some alternative embodiments, therapy system 10 may include an additional lead or lead segment (not shown in FIG. 1) that deploys one or more electrodes within the vena cava or other vein. These electrodes may allow alternative electrical sensing configurations to provide improved sensing accuracy in some patients. Accordingly, the lead and electrode configuration of FIG. 1 is provided for purposes of illustration and without limitation.

ICD 16 may sense electrical signals attendant to the depolarization and repolarization of heart 12 via electrodes (not shown in FIG. 1) coupled to at least one of the leads 18, 20, 22. In some examples, ICD 16 provides pacing pulses to heart 12 based on the electrical signals sensed within heart 12. The configurations of electrodes used by ICD 16 for sensing and pacing may be unipolar or bipolar.

ICD 16 also provides defibrillation therapy and/or cardioversion therapy via electrodes located on at least one of the leads 18, 20, 22. ICD 16 may detect arrhythmia of heart 12, such as fibrillation of ventricles 28 and/or 32, and deliver cardioversion or defibrillation therapy to heart 12 in the form of electrical shocks. In some examples, ICD 16 may be programmed to deliver a progression of therapies, e.g., pulses with increasing energy levels, until a tachyarrhythmia of heart 12 is stopped. ICD 16 may detect tachycardia or fibrillation employing one or more detection techniques known in the art.

In some examples, programmer 24 may be a handheld computing device, computer workstation, or networked computing device. Programmer 24 may include a user interface that receives input from a user. The user interface may include, for example, a keypad and a display, which may for example, be a cathode ray tube (CRT) display, a liquid crystal display (LCD) or light emitting diode (LED) display. The keypad may take the form of an alphanumeric keypad or a reduced set of keys associated with particular functions.

Programmer 24 can additionally or alternatively include a peripheral pointing device, such as a mouse, via which a user may interact with the user interface. In some aspects, a display of programmer 24 may include a touch screen display, and a user may interact with programmer 24 via the display. It should be noted that the user may also interact with programmer 24 or ICD 16 remotely via a networked computing device.

A user, such as a physician, technician, surgeon, electrophysiologist, or other clinician, may interact with programmer 24 to communicate with ICD 16. For example, the user may interact with programmer 24 to retrieve physiological or diagnostic information from ICD 16. A user may also interact with programmer 24 to program ICD 16, e.g., select values for operational parameters of ICD 16.

For example, the user may use programmer 24 to retrieve information from ICD 16 regarding the rhythm of heart 12, trends therein over time, or arrhythmic episodes. As another example, the user may use programmer 24 to retrieve information from ICD 16 regarding other sensed physiological parameters of patient 14, such as intracardiac or intravascular pressure, activity, posture, respiration, or thoracic impedance. As another example, the user may use programmer 24 to retrieve information from ICD 16 regarding the performance or integrity of ICD 16 or other components of system 10, such as leads 18, 20 and 22, or a power source of ICD 16.

The user may use programmer 24 to program a therapy progression, select electrodes used to deliver pacing and defibrillation pulses, select waveforms for the pacing and defibrillation pulses, or select or configure the fibrillation detection algorithm for ICD 16. As described in this disclosure, the fibrillation detection algorithm may employ techniques for identification and remediation of oversensed events, e.g., to avoid delivery of inappropriate shocks and to avoid inappropriate inhibition of pacing pulses, particularly due to oversensing caused by lead fracture noise.

Pacemaker dependent patients may not be paced during lead failure noise or may not capture the heart due to fractured conductors. With techniques for identification and remediation of oversensed events, in some cases, ICD 16 can deliver bradycardia pacing during ICD lead failure noise. Pacing can be timed to avoid pacing during a T wave or during actual ventricular fibrillation.

The user may also use programmer 24 to program similar aspects of other therapies provided by ICD 16, such as cardioversion or pacing therapies. In some examples, the user may activate certain features of ICD 16 by entering a single command via programmer 24, such as depression of a single key or combination of keys of a keypad or a single point-and-select action with a pointing device.

ICD 16 and programmer 24 may communicate via wireless communication using any techniques known in the art. Examples of communication techniques may include, for example, low frequency or radiofrequency (RF) telemetry, but other techniques are also contemplated. In some examples, programmer 24 may include a programming head that may be placed proximate to the patient\'s body near the ICD 16 implant site in order to improve the quality or security of communication between ICD 16 and programmer 24.

ICD 16 is an example of a device that may acquire, store and analyze near-field electrograms (NFEGMs) and far-field electrograms (FFEGMs). In particular, ICD 16 may detect cardiac events such as R waves in an NFEGM and identify whether the detected cardiac events are oversensed events based on one or more characteristics of an FFEGM. Such EGMs may be processed by ICD 16 to support identification and remediation of oversensed events.

ICD 16 may produce interval data indicating intervals between detection of various detected cardiac events. The detected cardiac events and interval data may be recorded in marker channel data along with cardiac events induced by the ICD, i.e., by delivery of pacing pulses, cardioversion shocks, or defibrillation shocks. The detected cardiac events define intervals that may be used by ICD 16 to control delivery of pacing, cardioversion, and/or defibrillation therapies to patient 12.

EGMs may be retrieved from ICD 16 by programmer 24, and displayed by programmer 24 for evaluation by a clinician or other user to, for example, determine whether a sensing integrity condition is present in ICD 16, leads 18, 20 and 22, or any other components of system 10. The EGMs may be considered in conjunction within other data, such as lead impedance data, which may also be stored by ICD 16, and retrieved and displayed by programmer 24.

FIG. 2 is a conceptual diagram illustrating a three-lead ICD 16 and leads 18, 20 and 22 of therapy system 10 in greater detail. Leads 18, 20, 22 may be electrically coupled to a stimulation module and a sensing module of ICD 16 via connector block 34. In some examples, proximal ends of leads 18, 20, 22 may include electrical contacts that electrically couple to respective electrical contacts within connector block 34 of ICD 16. Also, in some examples, leads 18, 20, 22 may be mechanically coupled to connector block 34 with the aid of set screws, connection pins, snap connectors, or other suitable mechanical coupling mechanisms.

Each of leads 18, 20, 22 includes an elongated insulative lead body, which may carry a number of concentric coiled conductors separated from one another by tubular insulative sheaths. Bipolar electrodes 40 and 42 are located adjacent to a distal end of lead 18 in right ventricle 28. In addition, bipolar electrodes 44 and 46 are located adjacent to a distal end of lead 20 in coronary sinus 30 and bipolar electrodes 48 and 50 are located adjacent to a distal end of lead 22 in right atrium 26. There are no electrodes located in left atrium 36 in the illustrated example of FIG. 2, but electrodes may be provided in left atrium 36 in alternative implementations.

Electrodes 40, 44, and 48 may take the form of ring electrodes, and electrodes 42, 46, and 50 may take the form of extendable helix tip electrodes mounted within insulative electrode heads 52, 54, and 56, respectively. In other embodiments, one or more of electrodes 42, 46, and 50 may take the form of small circular electrodes at the tip of a lead tine or other fixation element. Leads 18, 20, 22 also include elongated electrodes 62, 64, 66, respectively, which may take the form of an elongated coil that may be used to deliver cardioversion and/or defibrillation shocks. Each of the electrodes 40, 42, 44, 46, 48, 50, 62, 64, and 66 may be electrically coupled to a respective one of the coiled conductors within the lead body of its associated lead 18, 20, 22, and thereby coupled to respective ones of the electrical contacts on the proximal end of leads 18, 20, 22.

In some examples, as illustrated in FIG. 2, ICD 16 includes one or more housing electrodes, such as housing electrode 58, which may be formed integrally with an outer surface of hermetically-sealed housing 60 of ICD 16 or otherwise coupled to housing 60. In some examples, housing electrode 58 is defined by an uninsulated portion of an outward facing portion of housing 60 of ICD 16. Other divisions between insulated and uninsulated portions of housing 60 may be employed to define two or more housing electrodes. In some examples, housing electrode 58 comprises substantially all of housing 60. As described in further detail with reference to FIG. 4, housing 60 may enclose an electrical stimulation module that generates therapeutic stimulation, such as cardiac pacing pulses and cardioversion or defibrillation shocks, as well as an electrical sensing module for monitoring the rhythm of heart 12.

ICD 16 may sense electrical cardiac signals in the form of EGMs attendant to the depolarization and repolarization of heart 12 via electrodes 40, 42, 44, 46, 48, 50, 58, 62, 64, and 66. The electrical cardiac signals are conducted to ICD 16 from the electrodes via the respective leads 18, 20, 22 or, in the case of housing electrode 58, a conductor coupled to housing electrode 58. ICD 16 may sense such electrical signals via any bipolar combination of electrodes 40, 42, 44, 46, 48, 50, 58, 62, 64, and 66. Furthermore, any of the electrodes 40, 42, 44, 46, 48, 50, 58, 62, 64, and 66 may be used for unipolar sensing in combination with housing electrode 58.

Any multipolar combination of two or more of electrodes 40, 42, 44, 46, 48, 50, 58, 62, 64, and 66 may be considered a sensing electrode configuration forming a sensing vector. One example of a sensing vector formed by a sensing electrode configuration comprising a bipolar electrode combination on the same lead, such as the combination formed by tip electrode 42 and ring electrode 40 of lead 18. On one lead having three electrodes, there may be at least three different sensing electrode configurations available to ICD 16. For lead 18, these bipolar sensing electrode configurations are tip electrode 42 and ring electrode 40, tip electrode 42 and elongated coil electrode 62, and ring electrode 40 and elongated coil electrode 62.

In some cases, sense electrode configurations having electrodes on two different leads may be used. Further, as mentioned above, a sensing electrode configuration may utilize housing electrode 58, which may provide a unipolar sensing electrode configuration in combination with any of the electrodes on the lead. As an example, elongated coil electrode 62 and housing electrode 58 may provide a unipolar, coil-can sensing electrode configuration. In some examples, a sensing electrode configuration may comprise multiple housing electrodes 58. In any sensing electrode configuration, the polarity of each electrode may be configured as appropriate for the application of the sensing electrode configuration.

ICD 16 may deliver electrical stimulation therapy, such as pacing pulses or cardioversion or defibrillation shocks, via various stimulation vectors comprising different stimulation electrode configurations. In some examples, ICD 16 delivers pacing pulses via bipolar combinations of electrodes 40, 42, 44, 46, 48 and 50 to produce depolarization of cardiac tissue of heart 12. In other examples, ICD 16 delivers pacing pulses via any of electrodes 40, 42, 44, 46, 48 and 50 in combination with housing electrode 58 in a unipolar configuration.

Furthermore, ICD 16 may deliver defibrillation shocks to heart 12 via any combination of elongated coil electrodes 62, 64, 66 and housing electrode 58. Electrodes 58, 62, 64, 66 may also be used to deliver cardioversion pulses to heart 12. Electrodes 62, 64, 66 may be fabricated from any suitable electrically conductive material, such as, but not limited to, platinum, platinum alloy or other materials known to be usable in implantable defibrillation electrodes.

The configuration of therapy system 10 illustrated in FIGS. 1 and 2 is merely one example. In other examples, a therapy system may include epicardial leads and/or patch electrodes instead of or in addition to the transvenous leads 18, 20, 22 illustrated in FIG. 1. Further, ICD 16 need not be implanted within patient 14. In examples in which ICD 16 is not fully implanted in patient 14, ICD 16 may deliver defibrillation pulses and other therapies to heart 12 via percutaneous leads that extend through the skin of patient 14 to a variety of positions within or outside of heart 12.

In addition, in other examples, a therapy system may include any suitable number of leads coupled to ICD 16, and each of the leads may extend to any location within or proximate to heart 12. For example, other examples of therapy systems may include three transvenous leads located as illustrated in FIGS. 1 and 2, and an additional lead located within or proximate to left atrium 36. As another example, other examples of therapy systems may include a single lead that extends from ICD 16 into right atrium 26 or right ventricle 28, or two leads that extend into a respective one of the right ventricle 26 and right atrium 26. An example of this type of therapy system is shown in FIG. 3.

FIG. 3 is a conceptual diagram illustrating another example of therapy system 70, which is similar to therapy system 10 of FIGS. 1 and 2, but includes two leads 18, 22, rather than three leads. Leads 18, 22 are implanted within right ventricle 28 and right atrium 26, respectively. Therapy system 70 shown in FIG. 3 may be useful for providing defibrillation and pacing pulses to heart 12. Storage of EGMs according to the techniques described herein may also be performed by or with respect to system 70.

FIG. 4 is a functional block diagram illustrating one example configuration of ICD 16. In the example illustrated by FIG. 4, ICD 16 includes a processor 80, memory 82, electrical stimulation module 84, electrical sensing module 86, sensor 87, telemetry module 88, and power source 98. Memory 82 may includes computer-readable instructions that, when executed by processor 80, cause ICD 16 and processor 80 to perform various functions attributed to ICD 16 and processor 80 herein. Memory 82 may include any volatile, non-volatile, magnetic, optical, or electrical media, such as a random access memory (RAM), read-only memory (ROM), non-volatile RAM (NVRAM), electrically-erasable programmable ROM (EEPROM), flash memory, or any other digital media.

The various components of ICD 16 are coupled to power source 98, which may include a rechargeable or non-rechargeable battery. A non-rechargeable battery may be capable of holding a charge for several years, while a rechargeable battery may be inductively charged from an external device, e.g., on a daily or weekly basis. Power source 98 also may include power supply circuitry for providing regulated voltage and/or current levels to power the components of ICD 16.

Processor 80 may include any one or more of a microprocessor, a controller, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or equivalent discrete or integrated circuitry, including analog circuitry, digital circuitry, or logic circuitry. In some examples, processor 80 may include multiple components, such as any combination of one or more microprocessors, one or more controllers, one or more DSPs, one or more ASICs, or one or more FPGAs, as well as other discrete or integrated logic circuitry. The functions attributed to processor 80 herein may be embodied as software, firmware, hardware or any combination thereof.

In accordance with various aspects of this disclosure, ICD 16 may be configured to acquire a first cardiac signal via a first sense electrode configuration (e.g., an NFEGM signal), acquire a second cardiac signal via a second sense electrode configuration (e.g., a FFEGM signal), detect cardiac events in the first cardiac signal (e.g., R waves), identify at least some of the cardiac events detected in the first cardiac signal as oversensed events based on whether one or more characteristics (e.g., amplitude, slope, variability) of the second cardiac signal confirm the cardiac events, and control delivery of cardiac electrical stimulation therapy to a patient based on the identification of the oversensed events.

In some examples, ICD 16 may determine time intervals between the detected events that are not identified as oversensed events, and control delivery of electrical stimulation therapy to the patient based on the time intervals. In particular, ICD 16 may detect that one of the time intervals is greater than a threshold time interval, and deliver pacing therapy to the patient in response to the detection that one of the time intervals is greater than the threshold time interval. The pacing therapy may include first pacing therapy delivered via a first stimulation electrode configuration and second pacing therapy delivered via a second stimulation electrode configuration. The first and second stimulation electrode configurations may be formed by electrodes on the same lead or different leads, and may be positioned to deliver pacing to the same chamber or different chambers of the heart.

In some examples, ICD 16 may determine a count of a number of the time intervals that are shorter than a threshold time interval, detect that the count is greater than a threshold count, and deliver at least one of cardioversion or defibrillation therapy to the patient in response to the detection that the count is greater than the threshold count. In other examples, ICD 16 may detect that one of the time intervals is greater than a threshold time interval, deliver pacing therapy to the patient in response to the detection that one of the time intervals is greater than the threshold time interval, determine a count of a number of the time intervals that are shorter than a threshold time interval, detect that the count is greater than a threshold count, and deliver at least one of cardioversion or defibrillation therapy to the patient in response to the detection that the count is greater than the threshold count.

With further reference to FIG. 4, processor 80 controls electrical stimulation module 84 to deliver stimulation therapy to heart 12. Processor 80 may control electrical stimulation module 84 to deliver stimulation according to a selected one or more therapy programs, which may be stored in memory 82. For example, processor 80 may control electrical stimulation module 84 to deliver electrical pacing pulses or cardioversion or defibrillation shocks with the amplitudes, pulse widths, frequencies, or electrode polarities specified by the selected therapy programs.

Electrical stimulation module 84 is electrically coupled to electrodes 40, 42, 44, 46, 48, 50, 58, 62, 64, and 66, e.g., via conductors of the respective lead 18, 20, 22, or, in the case of housing electrode 58, via an electrical conductor disposed within housing 60 of ICD 16. Electrical stimulation module 84 is configured to generate and deliver electrical stimulation therapy to heart 12. For example, electrical stimulation module 84 may deliver defibrillation shocks to heart 12 via at least two electrodes 58, 62, 64, 66.

Electrical stimulation module 84 may deliver pacing pulses via ring electrodes 40, 44, 48 coupled to leads 18, 20, and 22, respectively, and/or helical tip electrodes 42, 46, and 50 of leads 18, 20, and 22, respectively. In some examples, electrical stimulation module 84 delivers pacing, cardioversion, or defibrillation stimulation in the form of electrical pulses or shocks. In other examples, electrical stimulation module 84 may deliver one or more of these types of stimulation in the form of other signals, such as sine waves, square waves, or other substantially continuous signals.

Electrical stimulation module 84 may include a switch module and processor 80 may use the switch module to select, e.g., via a data/address bus, which of the available electrodes are used to deliver pacing, cardioversion, or defibrillation pulses. The switch module may include a switch array, switch matrix, multiplexer, or any other type of switching device suitable to selectively couple stimulation energy to selected electrodes.

Electrical sensing module 86 monitors signals from electrode sensing vectors formed by different electrode sensing configurations. Electrode sensing configurations are defined by various combinations of electrodes 40, 42, 44, 46, 48, 50, 58, 62, 64 or 66 in order to monitor electrical activity of heart 12. For example, electrical sensing module 86 may acquire electrical cardiac signals in the form of NFEGMs and FFEGMs. Electrical sensing module 86 may include a switch module to select which of the available electrodes are used to sense the heart activity.

In some examples, processor 80 may select the electrodes that function as sense electrodes, or the sensing electrode configuration, via the switch module within electrical sensing module 86, e.g., by providing signals via a data/address bus. Electrical sensing module 86 may include multiple detection channels, each of which may comprise an amplifier. The detection channels may be configured to detect different cardiac events, such as P waves, R waves and the like. In response to the signals from processor 80, the switch module within electrical sensing module 86 may couple selected electrodes to each of the detection channels to acquire a desired EGM for detection of cardiac events.

If ICD 16 is configured to generate and deliver pacing pulses to heart 12, processor 80 may include pacer timing and control module, which may be embodied as hardware, firmware, software, or any combination thereof. The pacer timing and control module may comprise a dedicated hardware circuit, such as an ASIC, separate from other components of processor 80, such as a microprocessor, or a software module executed by a component of processor 80, which may be a microprocessor or ASIC.

The pacer timing and control module may include programmable counters which control the basic time intervals associated with DDD, VVI, DVI, VDD, AAI, DDI, DDDR, VVIR, DVIR, VDDR, AAIR, DDIR and other modes of single and dual chamber pacing. In the aforementioned pacing modes, “D” may indicate dual chamber, “V” may indicate a ventricle, “I” may indicate inhibited pacing (e.g., no pacing), and “A” may indicate an atrium. The first letter in the pacing mode may indicate the chamber that is paced, the second letter may indicate the chamber that is sensed, and the third letter may indicate the chamber in which the response to sensing is provided.




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stats Patent Info
Application #
US 20100106209 A1
Publish Date
04/29/2010
Document #
12260560
File Date
10/29/2008
USPTO Class
607 17
Other USPTO Classes
607 28
International Class
61N1/368
Drawings
12


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Bradycardia
Fibrillation
Ventricular Fibrillation


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Surgery: Light, Thermal, And Electrical Application   Light, Thermal, And Electrical Application   Electrical Therapeutic Systems   Heart Rate Regulating (e.g., Pacing)   Parameter Control In Response To Sensed Physiological Load On Heart  

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